This invention relates to a non-aqueous shaped explosive composition having a relatively high density and energy, formed when a hot solution of a self-explosive is emulsified with a surfactant-fuel mixture and the emulsion destabilizes upon cooling and aging. By "self-explosive" I refer to an organic material which can be detonated by itself, for example, with a conventional blasting cap. The self-explosive I use is a compound which contains at least one nitro- or nitramine group.
Prior art non-aqueous systems are referred to as melt-in-oil or melt-in-fuel emulsions such as disclosed in U.S. Pat. No. 4,248,644 in which the fuel or continuous phase contains a surfactant, and the molten oxidizer is dispersed throughout the fuel or continuous phase ("C-phase") by adequate agitation of the mixture which is then allowed to cool. The molten oxidizer is not a self-explosive, that is, it is a non-self-explosive (hereafter "oxidizer"). Upon cooling, the result is that the oxidizer forms an internal or discontinuous phase ("D-phase") of discrete droplets dispersed throughout the continuous (fuel) phase. This "stability" permits the droplets to supercool and remain more or less fluid or grease-like in texture at a temperature below that at which the emulsion was formed.
In the prior art, with very few exceptions, explosive compositions focus the criticality of a stable emulsion which prevents the self-explosive from recrystallizing. It was essential that the emulsion be stable and that no recrystallization of the non-self-explosive (oxidizer) occurred. If recrystallization occurred, the composition would fail to function as an explosive. In my invention, it is essential that there be recrystallization of the self-explosive after destabilization of the emulsion, or the composition would fail to function as a self-explosive.
For example, U.S. Pat. No. 4,566,919 discloses forming a melt or solution of ammonium nitrate in water, at a temperature above the salt crystallization temperature. The melt, or first solution, is then added to a solution of the emulsifier and an immiscible organic liquid fuel, while stirring, to produce a water-in-oil emulsion. The oxidizer is thus dispersed in the fuel phase, initially as droplets of solution at elevated temperature, and as the composition cools, the precipitation of the salts within the droplets is physically inhibited resulting in a stable emulsion with enhanced intimacy between oxidizer and fuel. In contrast, because the liquids are immiscible organic liquids, no water-in-oil emulsion is formed in my composition; the emulsifier is inert; the solvent in the D-phase and the liquid fuel in the C-phase are each essentially anhydrous, so that the emulsion formed is non-aqueous; and, the self-explosive is dissolved in the solvent phase.
More particularly, the emulsion from which the explosive of my invention is derived, is formulated at an elevated temperature, above that at which the self-explosive will crystallize from its solution (referred to herein as a "nitrosolution"). The emulsion consists essentially of a discontinuous nitrosolution phase (D-phase, for brevity) which is dipersed in a continuous phase of surfactant and fuel (C-phase, for brevity). The solution of self-explosive in organic solvent for the self-explosive is referred to herein as a "nitrosolution" because it is a single phase. The organic solvent for the nitro-containing or nitramine-containing self-explosive is referred to as a "nitrosolvent".
The surfactant-in-fuel C-phase consists essentially of at least two phases. The C-phase is a dispersion of surfactant and fuel. After forming the dispersion which is to provide the C-phase, the nitrosolution phase is added with vigorous mixing so as to homogeneously distribute the nitrosolution as the D-phase in the emulsion so formed. The emulsion is formed at a temperature above the recrystallization temperature. By "recrystallization temperature" I refer to the temperature at which crystals of self-explosive commence to form upon cooling a saturated solution of the self-explosive in essentially pure solvent.
The surfactant may function as the emulsifier, and vice versa. In those instances where the surfactant does not function as an emulsifier, an emulsifier is also added. It is essential that the surfactant and/or emulsifier be unreactive with the nitrosolvent, and therefore each is referred to as being substantially inert. Properly formulated, the composition is a thick, creamy or waxlike, pourable or pumpable emulsion which is poured while hot into a cavity and allowed to crystallize into a hard mass upon cooling to ambient temperature.
Heretofore, shapeable self-explosives (explosives) formed from self-explosives such as TNT, pentolite, composition B and the like, were prepared by a kettle procedure in which the material was melted and continuously mixed to ensure homogeneity, and the melt was then cast. But the cast melt shrunk upon cooling, suffered from gradient separation in those instance in which the cast melt was a blend (such as in composition B), and the skrinkage and separation was such that the characteristics of the explosive were generally less predictable than desired. Moreover, because of the sensitivity of TNT and other molten self-explosives, the process was not particularly safe at the elevated temperatures required for preparing the castable melt. The explosive of this invention uses a solution of the self-explosive which is substantially insensitive, making it safer to handle than prior art compositions. The pourable mixture (from which the explosive is derived) can be shaped in a molding cavity without significant shrinkage or gradient separation.